Fixed displacement fluid devices (e.g., motors and pumps) utilize displacement mechanisms for various purposes. For example, fixed displacement motors use displacement mechanisms to convert fluid pressure into a rotary output while fixed displacement pumps used displacement mechanisms to output a given amount of fluid in response to rotation of the displacement mechanism. Such devices are used in a variety of commercial applications. As a fixed displacement fluid devices, the displacement mechanism cannot be directly adjust to increase or decrease the amount of fluid transferred through the fluid device during one complete rotation of the shaft.
Variations in the amount of fluid transferred through the fluid device can be achieved, however, through the use of hydraulic flow control valves or a variable fluid supply (e.g., a variable displacement pump). However, in some applications, the use of hydraulic flow control valves or variable fluid supplies result in decreased efficiencies and/or added mechanical complexity.